Title of Invention

PARTICLE FILTER MADE OF METAL FOIL

Abstract A particle filter of metal foil having passages through which a fluid can flow and which are arranged in mutually juxtaposed relationship, wherein each passage has at least an inlet and an outlet, with a first passage and a second passage adjacent thereto, wherein the first passage has an open intake cross-section at a first end of the particle filter which extends at least partially into the first passage wherein the first passage has a closure means arranged opposite the intake cross-section towards a second end wherein - the closure means at least very substantially closes the first passage for the fluid which can flow there through, - at least one wall forming the first passage has perforations as filter openings to the second passage, - the second passage has an open discharge cross-section corresponding to the intake cross section, - the walls of the first passage and the second passage are of metal foil and - the filter openings form the sole intake to the second passage.
Full Text Particle filter made from metal foil
The present invention relates to a particle filter made from metal foil which has channels through which a fluid can flow and which are arranged adjacent to one another. Each channel has at least one inlet and an outlet. Furthermore, the particle filter has a first channel and a second channel which is adjacent thereto, the first channel having an open entry-cross section at a first end side of the particle filter. The invention also provides a process for producing a particle filter.
EP 0 134 002 has disclosed a diesel exhaust filter made from woven wire cloth and a process for its production. This diesel exhaust filter is constructed from layers which can be placed on top of one another or shaped helically to form an assembly. A layer comprises a corrugated or folded screening cloth and a planar, continuous or perforated covering layer. The two end faces of the diesel exhaust filter are designed in such a way that a closed end-face section lies opposite an open end-face section, an end-face section being closed by pinching. The corrugated or folded layer is for this purpose pressed onto the planar layer in folds.
It is an object of the present invention to provide a particle filter and a process for producing a particle filter which allow simplified production of the particle filter while at the same time also producing a large surface area in the particle filter.
This object is achieved by a particle filter made from metal foil having the features of claim 1 and by a process having
-1-
the features of claim 14. Advantageous refinements and features are given in the respective dependent claims.
A particle filter made from metal foil which has channels through which a fluid can flow and which are arranged adjacent to one another, each channel having at least one inlet and an outlet, with a first channel and a second channel which is adjacent thereto, the first channel having an open entry cross section at a first end side of the particle filter which extends at least partway into the first channel, the first channel, opposite the entry cross section, having a closure toward a second end side is distinguished by the fact that
- the closure at least as far as possible closes off the first channel to the fluid which can flow through,
- at least one wall which forms the first channel has perforations as filter passages leading to the second channel,
- the second channel has an open exit cross section which corresponds to. the entry cross section, and
- the walls of the first channel and of the second channel are made from metal foil.
The fact that the walls of the first and second channel are made from metal foil means that they each have a large surface area which comes into contact with the fluid. While when using a woven wire cloth only the individual filaments of the cloth are available as surface area, a wall which helps to form the first channel has a surface which is continuous apart from the perforations. The perforations, as filter passages leading to the adjacent second channel, also have a surface with which the fluid can come into contact. Therefore, compared to a woven wire cloth, a perforated wall of this type has a larger surface area which also has a larger active surface area for example either when provided with a suitable coating or when the material of the metal foil is selected appropriately. This
-2-
can be utilized for catalytic or other reactions or possible applications of a particle filter of this type.
This advantage of a large surface area is combined with the
advantage that a particle filter of this type can be produced
in a small number of working steps. The perforations required
are, for example, prefabricated in the metal foil. The
I corresponding shaping to form the individual channels is
advantageously completed in a single working step,
irrespective of whether or not the metal foil has
perforations. By way of example, it is advantageous if all the
walls which form the channels have perforations, so that
during production'the metal foils or the metal foil can be
processed independently of position and orientation.
Furthermore, perforating metal foil enables an accurate position of the filter passages to be achieved in the subsequent particle filter. while woven wire cloth, during processing, is at risk of filaments shifting, this is impossible in the case of perforations in the metal foil. This type of filter passages also enables the density of perforations to be varied over the metal £oil and therefore the channel wall which is to be formed, and also enables a diameter of such a perforation to be varied. This option can be employed in particular if different filter stages are to be formed in the particle filter.
To avoid a high pressure loss across the particle filter, the second channel has an open exit cross section which corresponds to the entry cross section. As a result, it is possible for the pressure loss to be set approximately proportionally to the number and dimensions of the perforations. According to an advantageous refinement, the particle filter has the closure of the first channel designed
-3-
in such a way that it does not allow any fluid to pass through. In this case, the filter passages form the only entry to the second channel. The closure of the first channel serves as a barrier wall, so that the fluid is forced through the filter passages. Particles contained in the flow of fluid which accumulate at the filter passages are then collected in the region of the closure. This can be assisted, for example, by providing a type of cage in the region of the closure. On account of the formation of the flow in the region of the closure, it is possible for a dammed region of the fluid formed at that location to be utilized in such a way that although particles do reach said region, they are then deposited in that region. Consequently, the filter passages remain clear and the particle filter requires fewer regeneration cycles. For regeneration, the particle filter may have suitable regeneration means, such as for example electrical heating, a catalytic coating or the like, in the region of the closure.
To simplify production of the particle filter, the first channel and the second channel are of the same design but are arranged in opposite directions to one another. This means that only one production tool is required for a metal foil; in the case of a particle filter of layered structure, all the metal foils can initially pass through production in one direction, and are only subsequently turned so that they alternate in opposite directions to one another. Advantageously, the first and second channels also form a honeycomb body which can preferably be produced in this way, with first and second channels alternating.
According to an advantageous refinement, the walls of the first and second channels are formed from a single metal foil. This enables the metal foil to be unwound from a roll of metal
-4-
foil, then subjected to a desired perforation step and for a desired shape to be imposed on the metal foil in the processing station which follows. The metal foil can then be formed into the particle filter either in wound or layered form. Only at this working step is it necessary for the metal foil to be cut off the roll of metal foil. The particle filter which has been layered or wound in this manner has joins at the locations where the individual walls touch one another, for example produced by brazing.
It is preferable to use a metal foil which has a coating before it is processed. This coating may either be of catalytic nature, with the result that the surface of the particle filter is once again increased in size considerably on account of the coating, or secondly the coating may also comprise a joining means, such as for example solder, in order for walls of the particle filter which are in contact with one another to be joined. For this purpose, by way of example the joining means is applied to the metal foil in strip form during or before the processing to form the particle filter. The joining means can also be applied, for example, to a suitable coating of the metal foil.
To increase the surface area of the particle filter, it has also proven advantageous if the first and/or second channel has a tapering cross section. This cross section is preferably in the shape of a wedge. For the first channel, the tapering cross section serves as an inlet and, as a result, reduces the pressure loss of the fluid flowing in. Furthermore, the active surface area which is acted on by fluid is increased in size, since the fluid flows onto the surface at an angle. At the same time, this arrangement enables particles which have accumulated at a filter passage to be, as it were, washed off by the fluid flowing onto the particles. As a result, the
-5-
particles which are to be filtered out are moved onward into the region of the closure of the first channel. This movement of the particles is assisted by the fact that opposite walls of the metal filter in each case have perforations. As a result, a laminar flow is formed along these walls, the fluid remaining in motion along this laminar flow. On account of turbulence formed in the central region of a channel of this type, the particles are carried onward, over the length of the channel, into the region of the channel closure, where they can be deposited.
A further important parameter of a particle filter is the pressure loss which it causes. However, to enable a large surface area to be formed in combination with a high filter action but without a high pressure loss, tests have shown that it is expedient to adapt the diameter of the filter passages. It has proven advantageous if the filter passage is a hole in the metal foil with a size of between 3 and 25 m, preferably 5 m. With a diameter of this type, it is possible to optimize these otherwise contradictory parameters. This is assisted if the particle filter has approximately between 80,000 and 120,000 filter passages per m2 of wall. The square meter of wall is in this case defined in such a way that the flowing fluid can flow onto it.
Since the particle filter, particularly when used in motor vehicles, is exposed to high temperatures, it is necessary for it to be thermally stable and also stable with respect to mechanical vibrations. This can be achieved with a metal foil which makes it possible to produce a wall with filter passages which is between 20 m and 65 m, preferably between 30 m and 40 m, thick. Particularly if the wall is between 30 m and 40 m, it is possible to produce the channels without major
-6-
outlay when producing a particularly lightweight particle filter which, nevertheless, has sufficient stability and strength in operation.
It has also proven advantageous if a coating of the particle filter has been applied after the channels have been produced
Furthermore, the invention provides a process for producing a particle filter from metal foil which can be used in particular to produce a particle filter as described above. The process involves the following steps:
- pulling metal foil out of at least one endless store,
- applying joining means, in particular in strip form, - shaping for subsequent channels in the metal foil,
- winding or stacking the metal foil, so that first channels and second channels arranged in opposite directions are formed, the first channel .having an open entry cross section at a first end side of the particle filter which extends at least partway into the first channel, the first channel, opposite the entry cross section, having a closure toward a second end side, and
- permanently joining contact surfaces of the channels which bear against one another, so that a particle filter is formed purely from metal foil.
According to an advantageous refinement, the process is developed further by coating the metal foil before or after the above steps. A further configuration of the process provides for the metal foil to be perforated before or after the above steps.
Further advantageous configurations and refinements and features of the invention are explained in more detail with reference to the following drawing, in which:
-7-
Fig. 1 shows a particle filter made from metal foil which is coated,
Fig. 2 shows a second particle filter which is made from a metal foil.
Fig. 3 shows a variation of the perforation in a metal foil of a particle filter, and
Fig. 4 shows a production line for the production of a particle filter from metal foil.
Fig. 1 shows a first particle filter 1. it has a first channel 2, a second channel 3 and a third channel 4. It is constructed from metal foils 5 which are layered on top of one another. The metal foils 5 form walls 6 of the channels 2, 3, 4. A first wall 7 and a second wall 8, which together form the first channel 2, have first perforations 9 as filter passages leading to the second channel 3 and third channel 4. A fluid 10 which flows through the particle filter 1, indicated by the arrows, enters an open entry cross section 11 at a first end side 12 of the particle filter 1. The entry cross section extends into the first channel 2. The fact that the first channel 2, opposite the entry cross section 11, has a closure 13 toward a second end side 14 means that the fluid is forced through the perforations 9. This is because a counterpressure, which forces the fluid 10 into the second channel 3 and the third channel 4, is built up at the closure 13. According to the embodiment illustrated, the closure 13 does not have any perforations and is therefore closed off in a gastight manner to the fluid 10 which can flow through. In another design (not shown here), the closure 13 also has perforations. This allows the fluid 10 to be guided through the entire length of the
-8-
first channel 2. According to a further advantageous configuration, perforations are provided only in a first region A of the closure 13, while there are no perforations in a second region B of the closure 13. As a result, the second region B, on account of the lack of flow in that region, acts as a dead space and a location for particles to accumulate in the first channel 2.
The second channel 3 has an open exit cross section 15, which corresponds to the open entry cross section 11 of the first channel 2. The open entry cross sections 11 and open exit cross section 15 illustrated in this figure have the advantage that, on account of their narrowing or increase in size, they act as nozzles or diffusors on the fluid 10. This contributes to minimizing pressure losses across the first particle filter 1. However, it is also possible for the exit cross section 15 to be larger than the entry cross section 11, with the result that the flow of fluid is slowed down. If, on the other hand, it is desired for the flow velocity to be increased downstream of the particle filter, the exit cross section 15 may also be smaller than the entry cross section 11.
Fig. 2 shows a second particle filter 16. The second particle filter 16 is produced from a metal foil 17. A particle-laden second fluid 18, indicated by the arrow, flows via a fourth channel 19, through second perforations 20, into a fifth channel 21. The metal foil 17 is folded in such a way that it forms third walls 22 of the channels 19, 21 and second closures 23. The cross section of the channels 19, 21 tapers. In a preferred configuration, the cross sections narrow in the shape of a wedge. In this way, it is possible to achieve a nozzle-like effect over the entire length of a channel and to increase the area of each channel onto which fluid flows.
-9-
Fig. 3 shows a part 24 of a metal foil with a variation of the third perforations 25. The density of the filter passages 26 increases over the length of the part 24. This can be achieved by changing the distances between the filter passages 26, as well as the number and diameter of these passages. As illustrated, a fluid, indicated by the arrow, advantageously flows onto the part 24. In the channel, the result is a flow which uses the entire length of the part 24.
Fig. 4 shows an advantageous production line 26 which can be used to carry out a process for producing a particle filter from metal foil, in particular a particle filter as claimed. For this purpose, a metal foil 29 is unwound from an endless store, in this case a roll of metal foil 28. In the next working step, a joining means 30 is applied to the metal foil 29. This advantageously takes place in strip form, expediently along those regions in which surfaces which subsequently rest on top of one another are in contact with one another and are to be joined to one another. In a further step, the subsequent channels of a particle filter are shaped. In the embodiment illustrated, this is carried out by means of a first press 31 and a second press 32. The first press 31 stamps the same geometry into the metal foil 28 as the second press 32. However, they are rotated through 180° with respect to one another. During the subsequent working step, the stamped geometries 33 are separated from the metal foil 29. The stamping which is offset alternately through 180° allows the geometries which have been stamped in this manner to be stacked continuously on top of one another. The stamping leads to first and second channels being formed, which are on the one hand of the same shape but on the other hand are arranged in opposite directions to one another. Then, in a working step which is not illustrated, contact surfaces which bear against one another are permanently joined to one another, for example
-10-
by means of grazing, so that a particle filter is formed purely from a metal foil. In the next working step of the production line 27, the particle filter 35 is perforated by means of a laser 34. Preferably, the particle filter 35 is provided, for example, with a catalytic coating before the perforation is made, a step which in turn increases the surface area of the particle filter 35.
11-
List of Reference Numerals
1 First particle filter
2 First channel
3 Second channel
4 Third channel
5 Metal foil
6 Walls
7 First wall
8 Second wall
9 First perforation
10 Fluid
11 Open entry cross section
12 First end side
13 Closure
14 Second end side
15 Open exit cross section
16 Second particle filter
17 Metal foil
18 Second fluid
19 Fourth channel
20 Second perforation
21 Fifth channel
22 Third walls
23 Second closures
24 Part
25 Third perforation
26 Filter passage
27 Working station
28 Endless store of metal foil (roll)
29 Metal foil
30 Joining means
31 First press
32 Second press
-12-
33 Stamped geometry
34 Laser
35 Particle filter
-13-
(14)
We Claims:
A particle filter (1,16,35) of metal foil (5,17,29) having passages (2,3,4,19,21) through which a fluid (10,18) can flow and which are arranged In mutually juxtaposed relationship, wherein each passage (2,3,4,19,21) has at least an tnlet and an outlet, with a first passage (2,19) and a second passage (3,4,21) adjacent thereto, wherein the first passage (2,19) has an open intake cross-section (11) at a first end (12) of the particle filter (1,16, 35) which extends at least partially into the first passage (2,19), wherert the first passage (2,19) has a closure mearts (13,23) arranged opposite the intake cross-section (11) towards a second end (14), wherein
- the closure means (13,23) at least very substantially closes the first passage (2,19) for the flukl (10,18) which can flow therethrough,
- at least one wall (7,8) forming the first passage(2,19) has perforations (9) as filter openings (26) to the second passage (3,4,21),
- the second passage (3,4,21) has an open discharge cross-section (15) corresponding to tfie intake cross section (11),
- the walls (6,7,8) of the first passage (2,19) and the second passage (3,4,19) are of metal foil (5,17,29) and
- the filter openings (26) form the sole Intake to the second passage (3.4,21).
A particle filter (1,16,35) as claimed in claim1 characterised in that the first passage (2,19) and the second passage (3,4,19) are of the same shape but are arranged in mutually opposite directions.
(15)
A particle filter 91,16,35)according to claim 1 or claim 2 characterised in that the first (2,19) and second (3,4,19) passages alternately form a honeycomb body.
A particle filter (1,16,35)according to clalm 1 or 2 characterised in that the walls of the first (2,19) and the second (3,4,19) passage are formed from a single metal foil (5,17,29).
A particle filter (1,16,35) according to claim 1 or 2 characterised in that the first (2,19) and /or the second (3,4,19) passage Is of a narrowing cross-section.
A particle filter (1,16,35) according to claim 5 characterised in that the narrowing cross-section is wedge-shaped.
A particle filter (1,16,35) according to claim lor 2 characterised in that the filter opening (6) is a hole in the metal foil (5,17,29) of a diameter of between 3 and 25 m, preferably 5 m,
A particle filter (1,16,35) according to claim 1 or 2 characterised in that the particle filter (1,16,35) has (approxlmately) between 80,000 and 120,000 filter openings (26) per square meter of wall (6).
A particle filter (1,16,35) according to claim 1 or 2 characterised in that a wall (3,4) with filter openings (26) is of a thickness of between 20 and 65
preferably between 30 and 40 m.
A particle filter (1,16,35) according to claim 1 or 2 characterised in that the particle filter (1,16,35) has a coating such as herein described.
(16)
A particle filter (1,16,35) according to claim 10 characterised in that the coating has been applied after production of the passages (2,3,4).
A particle filter (1,16,35) according to claim 1 or 2 characterised in that the perforations (9) have been formed after production of the passages (2,3,4).
A process for the production of a particle filter (1,16,35) of metal foil, in particular a particle filter (l,16,35) according to claim 1, comprising the following steps:
- drawing off metal foil from at least one endless store (28),
- applying joining agent (30), in particular in strip form,
- shaping for subsequent passages in the metal foil (29),
- winding on or stacking the metal foil (29) so that the mutually oppositely arranged first (2,19) and second (3,4,21) passages are formed, wherein the first passage (2,19) has an open intake cross-section (11) at a first end (12) of the particle filter (1,16,35) which extends at least partly into the first passage (2,19), wherein the first passage (2,19) has a closure means (13,23) arranged apposite the intake cross-section (11) towards a second end (14), and
permanently fining contact surfaces of the passages, which bear
against each other, so that a particle filter (1,16,35) is formed
solely from metal foil (28).
A process (according to) claim 13 characterised in that an operation of coating the metal foil (28) is effected prior to or after the steps recited in claim 13.
(17)
15. A process according to damn 13 or claim 14 characterised in that an operation of perforating the metat foil (28) is effected prior to or after the steps recited in claim 13 or claim 14.
Dated this 24th day of DECEMBER 2001
A particle filter of metal foil having passages through which a fluid can flow and which are arranged in mutually juxtaposed relationship, wherein each passage has at least an inlet and an outlet, with a first passage and a second passage adjacent thereto, wherein the first passage has an open intake cross-section at a first end of the particle filter which extends at least partially into the first passage wherein the first passage has a closure means arranged opposite the intake cross-section towards a second end wherein
- the closure means at least very substantially closes the first passage for the fluid which can flow there through,
- at least one wall forming the first passage has perforations as filter openings to the second passage,
- the second passage has an open discharge cross-section corresponding to the intake cross section,
- the walls of the first passage and the second passage are of metal foil and
- the filter openings form the sole intake to the second passage.

Documents:


Patent Number 208385
Indian Patent Application Number IN/PCT/2001/01353/KOL
PG Journal Number 30/2007
Publication Date 27-Jul-2007
Grant Date 26-Jul-2007
Date of Filing 24-Dec-2001
Name of Patentee EMITEC GESELLSCHAFT FUR EMISSIONS TECHNOLOGIE MBH.,
Applicant Address HAUPSTRASSE 150, D-53797 LOHMAR
Inventors:
# Inventor's Name Inventor's Address
1 MAUS WOLFGANG GUT HORST, D-51429 BERGISCH GLADBACH,
PCT International Classification Number B 01 D 46/52
PCT International Application Number PCT/EP00/04640
PCT International Filing date 2000-05-22
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 199 24 584.3 1999-05-28 Germany